Control devices of rotorcrafts

ABSTRACT

In a rotor control system of rotorcraft having variable pitch rotor blades and swash plate system which is controlled by the pilot&#39;&#39;s control stick and through which the cyclic pitch control and collective pitch control are effected, a link mechanism supported at a fulcrum is provided at least in the cyclic pitch control system and the position of said fulcrum is changed according to the forward flight speed of the rotorcraft, whereby the amount of longitudinal cyclic pitch change induced by the longitudinal control stick operation is decreased as the forward flight speed increases and concurrently the lateral cyclic pitch change is automatically imparted in the direction to compensate rolling motion of the rotorcraft, with the concomitant increase of said latter change as a function of the flight speed.

United States Patent [191 Yamakawa CONTROL DEVICES OF ROTORCRAFTS [75] Inventor: Eiichi Yamakawa, Kagamigahara,

Japan [73] Assignee: Kawasaki Jukogyo Kabushiki Kaisha, Kobe-shi, Japan [22] Filed: Mar. 17, 1972 [21] Appl. No.: 235,645

[30] Foreign Application Priority Data Apr. 6, 1971 Japan 46-21237 [52] US. Cl. 416/40, 416/114 [51] Int. Cl. B64c 27/74 [58] Field of Search 416/37, 40, 112-1 14, 416/1l 7-ll8 -[56] I 1 References Cited UNITED STATES PATENTS 2148,876 6/1956 Daland et al. .1 416/40 X 2,599,690 6/1952 Buivid et al..... 416/1 14 2,978,037 4/1961 Focke t 1 t 1 416/40 3,l99 60l 8/1965 Dean et a]. 416/1 12 3,217.80) 11/1965 Bossier .1 416/112 3,589,831 6/1971 Lemnios 416/40 X Mar. 26, 1974 FOREIGN PATENTS OR APPLICATIONS 995,459 8/1951 France ..4l6/4O l.l31,074 10/1956 France ..416/40 Primary Examiner-Everette A. Powell, Jr. Attorney, Agent, or Firm-William A. Knoeller [5 7] ABSTRACT whereby the amount of longitudinal cyclic pitch change induced by .the longitudinal control stick operation is decreased as the forward flight speed increases and concurrently the lateral cyclic pitch change is automatically imparted in the direction to compensate rolling motion of the rotorcraft, with the concomitant increase of said latter change as a function of the flight speed.

8 Claims, 10 Drawing Figures PATENTEUMARZB 1924 I v 3; 799 695 SHEEI 1 or s r a 59. d 5 my E PATENTEDMAR HM 9.799.695

SHEEI 3 OF 5 g I20 I00. I02 I04 I02 HI PATENTEUHARZB 4974 SHEEI 0F 5 FIG. 5

This invention relates to a rotor control device of aircraft having a rotor system, such as helicopters, compound helicopters or composite aircraft.

In general, a rotor system of rotary wing aircraft comprises variable pitch rotor blades and swash plate system, which is controlled by a flight control system of the aircraft and through which the cyclic pitch control and collective pitch control are effected. During forward flight, when nose-up longitudinal control stick operation is performed, the response to such operation becomes more sensitive as the flight speed increases and concurrently rightward rolling motion occurs which also increases with the flight speed. Therefore, in order to obtain optimum amount of pure pitching motion, it is necessary to decrease the amount of the longitudinal control stick operation and concurrently it is necessary to increase the amount of the lateral corrective control stick operation to the left as the forward flight speed of the aircraft increases. Adding to those control characteristics, the nose-up longitudinal control stick operation during high speed flight results in upward flow through the rotor disk, which causes abrupt increase of the vibratory load on the blade due to increase of the angle of attack, and sometimes rotor blades can be driven into stalled condition. Therefore, at the time of nose-up longitudinal control stick operation it is also necessary to give corrective control input to decrease the angle of attack of the rotor blades by moving collective pitch control stick downwardly and the amount of said corrective control input should be increased with the forward flight speed of the aircraft.

On the other hand, when the lateral control stick operation is performed, the effect of such operation is essentially independent of the forward flight speed and no pitching motion is induced. Therefore, in order to obtain a certain amount of pure rolling motion, it is only necessary to give a certain amount of lateral control stick operation independently of the forward flight speed. When the collective pitch control stick is moved upwardly, nose-up pitching motion and right rolling control characteristics and the amounts of corrective control inputs during maneuvers vary as a function of the flight speed, and the control of rotorcraft becomes extremely difficult particularly during high speed flight.

The present invention aims to solve these problems of the rotorcraft.

The present invention is applicable to the rotor control system of rotorcraft having variable pitch rotor blades and swash plate system which is controlled by the pilots control stick and through which the cyclic pitch control and collective pitch control are effected. This invention is characterized by that a link mechanism supported as a fulcrum is provided at least in the cyclic pitch control system and the position of said fulcrum is changed according to the forward flight speed of the rotorcraft, whereby the amount of the longitudi- 2 nal cyclic pitch change induced by the longitudinal control stick operation is decreased as the forward flight speed increases and concurrently the lateral cyclic pitch change is induced as a corrective control action to compensate rolling motion which is induced by the longitudinal control stick operation, and the amount of said latter change is increased as a function of the flight speed.

Besides the above mentioned characteristics, this invention has another aspect which enables the collective pitch angle to be also changed by the longitudinal controlstick operation and the amount -of said change is a function of the flight speed.

Furthermore, this invention enables to give the cor rective control inputs to change both longitudinal and lateral cyclic pitch angles simultaneously in the case of collective pitch control stick operation and the amount of said corrective'control inputs are changed as a function of the forward flight speed of the rotorcraft.

FIG. 1 is a perspective view schematically showing an example of the rotor system to which the present invention is applicable;

FIG. 2 is a schematic view showing an embodiment of the present invention; 7

FIGS. 3a and 3b are views for explaining the 'operation of the mechanism shown in FIG. 2;

FIG. 4 is a schematic view showing another embodiment of the invention;

FIG. 5 is a perspective view schematically showing another example of the rotor system to which the present invention is applicable; and

FIGS.'6a, 6b, 6c and 6d are schematic views showing different embodiments of the invention respectively.

A preferred embodiment of the invention will be described hereunder with reference to the drawings. Referring first to FIG. 1, there is shown an example of rotor system to which the present invention is applicable, and control sticks 10 are pivotally connected to a torque tube 12 by means of pins 11 respectively. The torque tube 12 is supported by brackets 13 in such a manner that it is rotatable but not movable axially. The torque tube 12 is formed with a downwardly projecting lever 14 and one end of a longitudinally extending push rod 15 is connected to said lever. The other end of the push rod 15 is connected to a vertical arm of a bell crank 16. A lever 18 is secured to the bell crank 16 through the intermediate block 17, and the length of lever 18 is equal to. but extending in the opposite direction to a horizontal arm of said bell crank.

The lower ends of the two control sticks 10 are interconnected by a push rod 21 and further the lower end of one control stick 10 is connected to one end of a bell crank 23 by a push rod 22. The bell crank 23 is supported by a bracket 24 and one end of a push rod 25 is connected to the other end of said bell crank 23. The other end of the push rod 25 is connected to one end of a bell crank 26 and a horizontal arm of said bell crank 26 is equal in length to the horizontal arm of the bell crank 16 and the lever 18. Reference numeral 31 designates a pair of collective pitch control sticks which are connected with each other by a horizontal rod member 32. The horizontal rod member 32 is supported by brackets 33 in such a manner that it is rotatable but not movable axially. A bell crank support 34 is fixed to the horizontal rod member 32 projecting forwardly therefrom and on which the bell crank 16, the block 17 and the bell crank 26 are pivotably supported.

Reference numeral 50 designates a swash plate. The stationary part 51 of the swash plate 50, as is well known, is vertically movable relative to a mast 53 and rotatable about an optional horizontal axis passing the center of said swash plate, and is connected to the lever 18 and the bell crank 16 by push rods 20 and 40 at the diametrically opposite points on a line A A respectively and is connected to the bell crank 26 by a push rod 30 at a point on a line B-B perpendicular to the line AA. Thus, it will be understood that the angle of inclination of the stationary part 51 of the swash plate 50 will be changed about the line BB by moving the control sticks in the directions indicated by the solid line arrows and will be changed about the line AA by moving the same in the directions indicated by the broken line arrows. It will also be understood that the stationary part 51 will be moved upwardly by moving the collective pitch control sticks 31 upwardly. On the stationary part 51 is rotatably supported the rotating 'part 52 to which are connected pitch horns 55, provided at the leading edge of each rotor blades 56, through pitch links 54. Further, the rotor blades 56 are supported by the mast 53 through a spindles 57, in such a manner that the pitch angle thereof may be changeable. Therefore, itwill be understood that, when the control sticks 10 are moved forward or backward as indicated by the solid line arrow, swash plate 50 is inclined about the line BB, with one side thereof located above and the other side below the line AA. Therefore, the pitch angle of the rotor blades 56 become largest or smallest on a line a-c and the rotor is inclined about the line a-c due to its gyroscopic-effect. Likewise, when the control sticks 10 are moved laterally in the direction indicated by the broken line arrow, the rotor is inclined about a line b-d. When the collective pitch control sticks 31 are moved upwardly, the pitch angle of the rotor blades 56 are increased as a whole.

The above-described mechanism is already known. The present invention can be applied to portions (a) and (b) of such mechanism. An example in which the present invention is applied to the portion (a) of the mechanism is shown in-FIG. 2. In FIG. 2, parts corresponding to those in FIG. 1 are indicated by same numerals.

With reference to FIG. 2, the upper end of the push rod. is not connected directly to the stationary part 51 of the swash plate but connected to one end of a lever 104. The lever 104 has-a slot 105 and a fulcrum pin 103, provided at the free end of an arm 102 of a servo 101 which is controlled by a suitable electronic device 100, is engaged in said slot. A push rod 120 has one end connected to the lever 104 at a point intermediary of the point of connection between the upper end of the push rod 20 and said lever 104, and the slot 105. The other end of the push rod 120 is connected to an input side of a hydraulic booster 220. An output shaft 320 of the hydraulic booster 220 is connected to the periphery'of the stationary part 51 of swash plate The electronic device 100 -is a device to detect the flight speed and operate the servo 101 according to the detected flight speed, and may be constructed with known technics.

The other end of the lever 104 is connected to a fixed bracket 107 by a rod 106. A lever 108 has one end connected to the upper end of the push rod and the other end to the right hand end portion of the lever 104 by a pin 111. The pin 111 is locatedjust below the right hand end of the slot 105. A push rod 130 has the lower end connected to the mid portion of the lever 108 to give an input to a hydraulic booster 230. An output shaft 330 of the hydraulic booster 230 is connected to the stationary part 51 of swash plate. The upper end of the push rod 40 is connected to one end of a lever 109, the other end of which is supported by a fixed bracket 110, to move the stationary part 51 of swash plate through a push rod 140, having the lower and connected to the mid portion of said lever 109, through a hydraulic booster 240 and through an output shaft 340 of said hydraulic booster. The length ratios of the levers 104, 108 and 109 are as shown in FIG. 2.

FIGS. 3a and 3b illustrate the operation of the mechanism shown in FIG. 2. FIG. 3a shows the mechanism in the state of the flight speed is zero or in the hovering condition and FIG. 3b shows the mechanism in the state of the maximum flight speed. Namely, in the hovering condition, the fulcrum pin 103 is located at the right hand end of the slot l05 and just above the pin 111. Therefore, when the control sticks are moved in the longitudinal direction for nose-up motion of the rotorcraft, in this case, the upward movement of the rod 120 relative to the movement of the rod 20 is largest and equal to the downward movement of the rod 140. The rod 130 remains stationary unless the rod 30 is moved by the lateral movement of the control sticks, so that no corrective control in the lateral direction will be effected during the longitudinal control stick operation. The upward movement of the collective pitch control sticks causes the equal amount of upward movement of the rods 120, 130 and 140. Therefore, in the hovering condition, the operation of the present invention is not different at all from the operation of the ordinary system shown in FIG. 1. At the maximum flight speed, on the other hand, the fulcrum pin 103 is located close to the left hand end of the slot and, when the longitudinal control sticks are pulled in the backward direction, the upward movement of the rod relative to the movement of the rod 20 is smallest and the nose-up cyclic pitch change is smaller than that in the case of hovering. At the same time, a downward movement of the rod occurs, resulting in a lateral corrective control input in the left rolling direction. Since the upward movement of the rod 120 is smaller than the downward movement of the rod 140, the center of the swash plate system moves downwardly, so that corrective control to decrease the collective pitch angle also effected as a result of the pull back operation of the longitudinal control sticks. When the control sticks are moved in the lateral direction, the lever 108 pivots about the pin 111 and the movement of the rod 130 relative to the movement of the rod 30 is constant irrespective of the flight speed, and no corrective control input in the other directions will be induced. The upward movement of the collective pitch control sticks causes the equal amount of upward movement of the rods 20, 30 and 40 but the amount of the movement of rod 120 and the amount of the movement of rod 130 are smaller than the amount of upward movement of the rod 140, so that the longitudinal corrective control for nose-down direction and lateral corrective control in the left rolling direction are induced. The amount of corrective control inputs relative to the flight speed can be determined from the flight characteristics of rotorcraft by properly designing the characteristics of the electronic device 100.

In the present invention, the above-described construction can also be employed at the portion (b) of FIG. 1; In this case, the intended object of this invention can be sufficiently achieved, although the corrective input of the collective pitch by the movement of the longitudinal control sticksand the corrective inputs in the longitudinal and lateral directions by the movement of the collective pitch control sticks cannot be obtained. It is to be understood that, in the present invention, the rods 320, 330 and 340 are not necessarily connected to the periphery of the stationary part 51 of swash plate. For instance, the rod 340 may be connected to a radially inward point of the swash plate as shown in FIGS. 4a and 4b. In this case, the length ratio of the lever 18 and the horizontal arm of bell crank 16, for example, may be varied in proportion to the radial positions of the points of connection of the rods 320 and 340to the stationary part 51.

The present invention is applicable, not only to the type of rotor system shown in FIG. 1 but also to other types of rotor system, and an example thereof is shown in FIG. 5. In the mechanism shownin FIG. 5, the lower end of the push rod 40 is connected toa lug 35 fixed to the bell crank support 34, and the upper end thereof is connected not directly to the stationary part 51 of swash plate but to the mid portion of a lever 41 which is supported at one end by a fixed bracket 42. The other end of the lever 41 is connected to the lower end of a rod 58 supporting the center of the swash plate. In this case, the intended object of this invention can be sufficiently achieved, although the corrective input of the collective pitch during the movement of longitudinal control sticks cannot be obtained.

FIGS. 6a, 6b, 6c and 6d respectively show modifications of the control device according to the invention. In FIG. 6a, the fulcrum pin 103 is supportedby a spring cartridge 113 through an arm 112 and moved by the servo 101 against the force of the spring but is returned to a predetermined position by said spring when the servo fails. In FIG. 612, there are provided two of the system composed-of theelectronic device and servo, as indicated at 100a, l00b and 101a, 101b, and one of them operates when the other fails. In FIG. 60, an output shaft 131 of the servo 101 is connected to the mid portionof a rod132 which is pivotally connected at one end to a fixed bracket 133 and the fulcrum pin 103 is provided at the other end of said rod 132. In FIG. 6a, the slot 105 is a cam slot having a suitable shape.

According to the present invention, the control characteristics of the rotorcraft during maneuvers can be improved as described above, but in addition, the position characteristics of the control sticks during steady horizontal flight can also be improved Namely, in a compound helicopter the propulsive force is generated by the propeller and the major part of lift force is generated by the main wing, in order to minimize the load on the main rotor during high speed flight. Therefore, the collective pitch angle is decreased with the flight speed increases and, above a certain speed, the longitudinal cyclic pitch angle necessary for steady horizontal flight must be increased in the nose-up direction with the flight speed increases. As a result, the so-called stick reversal phenomenon occurs in which the control sticks move once forward as the flight speed increases and then move backward as the-flight speed increases.

With the control device of this invention, the rotor system can be designed] such that the cyclic pitch angle 6 in the nose-up direction can be automatically obtained when the collective pitch control sticks are moved downwardly, as described above, and hence the stick reversal tendency can be eliminated.

In a pure helicopter, on the other hand, both the propulsive force and lift force need to be generated by the main rotor, and therefore, in orderto overcome the drag force of fuselage and obtain a high speed, it becomes necessary to tilt the rotor disk forwardly and increase the propulsive force, by imparting a nose-down cyclic pitch angle. Consequently, it is necessary to increase the collective pitch angle with the flight speed and concurrently move the longitudinal control sticks excessively forward. In such a helicopter, the maximum flight speed is limited because little margin of stroke is left for forward movement of the longitudinal control sticks. Such disadvantage can also be overcome by the present invention because, with the control device of this invention, the rotor system can be designed such that a cyclic pitch angle in the nose-down direction may automatically be imparted by the upward movement of the collective pitch control sticks.

Although the present invention has been described and illustrated herein in terms of a preferred embodiment and various modifications'thereof, it should be understood that the invention is not restricted to the specific embodiments but many changes and modifications are of course possible without deviating from the spirit of the invention.

What is claimed is:

l. A control system for use in rotary wing aircraft having variable pitch rotor blades coupled to a swashplate mechanism through which pitch control of said blades is'effected, comprising:

a manually operable control member for effecting cyclic pitch control of said blades;

first and second shifting members coupled to said swashplate mechanism. for shifting said swashplate mechanism about first and second different axes of rotation, respectively; i

a first linking member having first and second arms located on opposite sides of a movable axis of rotation; Y means coupling said first shifting member and said manual control member to one arm of said first linking member, said first linking member being pivoted about its axis of rotation in response to movement of said control member;

a second linking member pivotally coupled to the other arm of said first linking member, said second shifting member being coupled to said second linking member;

a fulcrum member coupled to said first linking member for shifting the axis of rotation thereof to thereby change the effective lengths of said first and second arms; and

means responsive to the airspeed of said aircraft for moving said fulcrum member relative to said first linking member to shift the axis of rotation of the latter.

2. The control system according to claim 1, wherein said fulcrum member is movable by said airspeed responsive means over a predetermined distance to move said movable axis of rotation between first and second end positions and said second linking member is pivotally coupled to said first linking member adjacent said first end position such that when said movable axis of rotation is located at said first end position, said second linking member exhibits minimal pivoting movement in response to pivoting movement of said first linking member and when said movable axis of rotation is in said second end position said second linking member exhibits maximal pivoting movement in resonse to pivoting movement of said first linking member.

I 3. The control system according to claim 2, wherein said manual control member is movable in first and second different directions and said means coupling said manual control member to said first linking member comprises a first linkage mechanism for translating movement of said control member in its first direction into a rotational movement of said first linking member about its movable axis of rotation; said system further comprising a further linkage mechanism coupling said control member to said second linking member for translating movement of said control member in its second direction into a rotational movement of said second linking member about its pivotal coupling to said first linking member.

4. The control system according to claim 3, further comprising a first linkage rod connected at one end to said one arm of said first linking member, and means coupling the other end of said first rod to said manual control member; wherein said first shifting-member is connected to said one arm between said movable axis of rotation and the connection of said first rod and said first linking member; and wherein said further linkage mechanism comprises a second linkage rod connected at one end to said second linking member, said second shifting member being connected to said second linking member between the pivotal coupling of said first and second linking members and the connection of said second rod to said second linking member.

5. The control system according to claim 4, wherein the distance between said linking member pivotal coupling and said second rod connection with said second linking member is substantially the same as the distance between said linking member pivotal coupling and said first rod connection with said first linking member.

6. The control system according to claim 5, wherein the distance between said linking member pivotal coupling and said first shifting member connection with said first linking member is substantially the same as the distance between said linking member pivotal coupling and said second shifting member connection with said second linking member.

7. The control system according to claim 1, wherein said first and second axes of rotation of said swashplate mechanism are substantially orthogonal to each other.

8. The control system according to claim 1, further comprising a second control member coupled to said swashplate mechanism for shifting the swashplate axially in a direction substantially orthogonal to the plane defined by said first and second axes of rotation of said swashplate mechanism. 

1. A control system for use in rotary wing aircraft having variable pitch rotor blades coupled to a swashplate mechanism through which pitch control of said blades is effected, comprising: a manually operable control member for effecting cyclic pitch control of said blades; first and second shifting members coupled to said swashplate mechanism for shifting said swashplate mechanism about first and second different axes of rotation, respectively; a first linking member having first and second arms located on opposite sides of a movable axis of rotation; means coupling said first shifting member and said manual control member to one arm of said first linking member, said first linking member being pivoted about its axis of rotation in response to movement of said control member; a second linking member pivotally coupled to the other arm of said first linking member, said second shifting member being coupled to said second linking member; a fulcrum member coupled to said first linking member for shifting the axis of rotation thereof to thereby change the effective lengths of said first and second arms; and means responsive to the airspeed of said aircraft for moving said fulcrum member relative to said first linking member to shift the axis of rotation of the latter.
 2. The control system according to claim 1, wherein said fulcrum member is movable by said airspeed responsive means over a predetermined distance to move said movable axis of rotation between first and second end positions and said second linking member is pivotally coupled to said first linking member adjacent said first end position such that when said movable axis of rotation is located at said first end position, said second linking member exhibits minimal pivoting movement in response to pivoting movement of said first linking member and when said movable axis of rotation is in said second end position said second linking member exhibits maximal pivoting movement in resonse to pivoting movement of said first linking member.
 3. The control system according to claim 2, wherein said manual control member is movable in first and second different directions and said means coupling said manual control member to said first linking member comprises a first linkage mechanism for translating movement of said control member in its first direction into a rotational movement of said first linking member about its movable axis of rotation; said system further comprising a further linkage mechanism coupling said control member to said second linking member for translating movement of said control member in its second direction into a rotational movement of said second linking member about its pivotal coupling to said first linking member.
 4. The control system according to claim 3, further comprising a first linkage rod connected at one end to said one arm of said first linking member, and means coupling the other end of said first rod to said manual control member; wherein said first shifting member is connected to said one arm betweEn said movable axis of rotation and the connection of said first rod and said first linking member; and wherein said further linkage mechanism comprises a second linkage rod connected at one end to said second linking member, said second shifting member being connected to said second linking member between the pivotal coupling of said first and second linking members and the connection of said second rod to said second linking member.
 5. The control system according to claim 4, wherein the distance between said linking member pivotal coupling and said second rod connection with said second linking member is substantially the same as the distance between said linking member pivotal coupling and said first rod connection with said first linking member.
 6. The control system according to claim 5, wherein the distance between said linking member pivotal coupling and said first shifting member connection with said first linking member is substantially the same as the distance between said linking member pivotal coupling and said second shifting member connection with said second linking member.
 7. The control system according to claim 1, wherein said first and second axes of rotation of said swashplate mechanism are substantially orthogonal to each other.
 8. The control system according to claim 1, further comprising a second control member coupled to said swashplate mechanism for shifting the swashplate axially in a direction substantially orthogonal to the plane defined by said first and second axes of rotation of said swashplate mechanism. 